Hydro-cyclone separator for a system for separating algae and other contaminants from a water stream

ABSTRACT

A method and apparatus for treating raw influent water to remove particles, algae and toxic chemicals from the water. Basically, air is dissolved in recirculated water under high pressure in an air contactor unit, the air saturated water is intimately mixed with the raw, particle bearing, water in a particle mixing system, and the water, particle and air mixture is passed through an air bubble separator wherein bubbles formed when the pressure on air saturated water is reduced carry away toxic gases and particulate material. If desired for further cleaning the water can be sent through a second series of air contactor, particle mixer and air bubble separation, but with a gas comprising ozone to further remove suspended particles and non-volatile dissolved organic matter. In order to improve mixing of the particles and the air saturated water passing through tubes, preferably a pattern of dimples is formed on at least part of the interior wall of the tubes. Upon completion of the process the water is ready for use or for further filtration in a conventional filtration plant.

FIELD OF THE INVENTION

[0001] This invention relates in general to systems for removingcontaminants from liquids and, more specifically to a system forremoving volatile gases, pesticides and particles such as algae, othersuspended organic solids, dissolved oils and other particles includinglarge and heavy particles and light, fine or buoyant particles fromwater.

BACKGROUND OF THE INVENTION

[0002] Water supplies for domestic drinking water, process water forchemical plants or other liquids are often contaminated with a varietyof contaminants, such as toxic chemicals, algae, dissolved oil andvarious organic and inorganic particles of various sizes. Thesecontaminants must be removed in a reliable, cost effective manner.

[0003] Many older water treatment plants use gravitational separationmethods, typically in sedimentation systems or dual-media sandfiltration systems that may not be acceptable under the newer waterquality standards. In some cases, these systems can meet the standardsthrough the use of properly mixed polymer chemical filter aids. Therequired expensive and complex polymer chemical mixing equipmentrequires constant attention, since the amount of the chemicals beingadded to raw water must be frequently readjusted to match thecontinually changing chemistry of the water being filtered. Slow sandfilters require a considerable investment, but generally can be operatefor longer periods without cleaning. Unfortunately, even withpretreatment, both dual-media and slow sand filters fail to meet waterquality standards for hours or several days after each backwashcleaning.

[0004] Ordinary chemical flocculation and sedimentation processes do notprevent toxic chemicals, pesticides and algae from passing through theordinary filter bed. If algae spores are present when chlorine is added,toxic disinfection byproducts are formed, which is highly undesirableand a violation of the USEPA Safe Drinking Water Act. The inability ofolder municipal filtrations systems to remove algae is apparent in thelack of clarity found when a swimming pool is filled with “clean” tapwater. Most pool contractors have to shock tap water with large doses ofchlorine chemical pool oxidizer to achieve the desired clear pool waterappearance.

[0005] Particulate material has also been removed from liquids byfloatation, another gravitational method, in which bubbles of a gas,such as air or oxygen, are introduced into the lower levels of theliquid and float to the top, carrying fine particles with them. Variouschemical additives, such as flocculation aids, typically alum polymers,are required with these systems. Flotation is a gravitational methodbecause the rise of bubbles is due to the gravitational accelerationacting on the mass of the liquid in accordance with the basic forceequals mass time acceleration relationship. A force balance relative toa pocket of gas phase within liquid (a bubble), where the mass of thebubble is its volume times its density, shows that the bubble must riseto find equilibrium, because the density of a gas is generally less thanthat of a liquid. Large flotation tanks are required to allow adequatetime for air bubbles to reach the surface.

[0006] Failure to remove algae prior to filtration also leads to cloggedfilters, increases filter operation costs and wastes water required forfrequent filter cleaning cycles. The use of flocculation promotingchemicals increases the volume of sludge to be dewatered and removed.

[0007] Thus, there is a continuing need for a separation system thatwill rapidly and efficiently remove particles and volatile gases fromliquids while treating a liquid, will efficiently remove algae andvolatile gases such as MTBE during pretreatment prior to filtration andwill reduce overall treatment costs and conserves water through lessfrequent filter cleaning and a smaller sludge volume.

SUMMARY OF THE INVENTION

[0008] The above noted problems, and others, are overcome in accordancewith this invention by a particle separation system that includes apretreatment section for economically removing algae and othercontaminates prior to filtration. The pretreatment includes injectingmillions of extremely small air bubbles per liter into the incoming rawwater. This dissolved air flotation technology increases a plants dailycapacity and reduces the potential formation of toxic chlorine-chemicaland post-treatment byproducts.

[0009] Initially, recirculated plant output water under high pressureand air under high pressure are mixed in a an air contactor element,generally consisting of one tank or two or more tanks in series.Preferably, the tank contains a suitable media that provide a highsurface areas that increases adsorption of air into the water. Allpressures referred to hereinafter are gauge pressures.

[0010] The air saturated recirculated water enters a particle mixingsystem where it is mixed with raw influent water. The mixed water passesalong a tubular spiral to cause intimate mixing. Preferably, a patternof dimples is provided on at least part of the inner wall of the spiraltube, to increase flow turbulence and assure optimum mixing.

[0011] The mixed water then passes to an air bubble separator unit wherea toroidal flow is induced as the water moves upwardly in the unit,producing a vortex that cause air to move to the center and form anelongated axial air column with the water rotating between the vesselwall and the air column. Heavy solid particles drop to the bottom of theunit. Water largely cleaned of algae and other light particles exitsnear the top of the unit, with light float particles being removedadjacent to the top of the unit. Air and volatile gases exit at the verytop of the unit.

[0012] The cleaned water from this air bubble separation unit may beused for many purposes. However, in some cases further removal of thesmall amount of remaining contaminates is desirable. In that casecleaned water from the air bubble separator then passes to a second aircontactor element at a lower, but above atmospheric, pressure. Oxygen,preferably containing a suitable quantity of ozone, is then absorbed orforced into the air contactor tank under pressure higher than the waterpressure. The water now containing a suitable quantity of dissolvedoxygen/ozone passes to a second particle mixing system similar to thefirst particle mixing system as described above. As the process waterenters the second particle mixing system, hydroxyl radicals(dissolvedozone) are mixed with the remaining suspended particles and non-volatiledissolved organic matter.

[0013] Water from the second particle mixing system then passes to asecond air bubble separator, similar to the first one as describedabove. Bubbles with microscopic suspended particles coalesce along theunit centerline due to the vortex effect and are extracted at the top ofthe unit. The process water, now further cleaned of algae and otherorganic particles, may proceed to any desired conventional filtrationsystem, where any remaining heavy solid particles are removed. Since thepretreatment system removes over 85% of the suspended solids in theoriginal untreated water, filter cycles will be much longer than before,with much lower operating and filter maintenance costs.

BRIEF DESCRIPTION OF THE DRAWING

[0014] Details of the invention, and of preferred embodiments thereof,will be further understood upon reference to the drawing, wherein:

[0015]FIG. 1 is a schematic flow diagram, partially in section, of afirst embodiment of the pretreatment particle separation system;

[0016]FIG. 2 is a perspective view of the particle mixing system;

[0017]FIG. 3 is a perspective view of the air bubble separator;

[0018]FIG. 4 is an axial section view of the upper portion of the airbubble separator of FIG. 4;

[0019]FIG. 5 is an axial section view of the lower portion of the airbubble separator of FIG. 4;

[0020]FIG. 6 is a schematic flow diagram, partially in section, of asecond embodiment of the pretreatment particle separation system;

[0021]FIG. 7 is a detail elevation view, partially cut away, of analternate preferred air contractor flow arrangement;

[0022]FIG. 8 is a detail cross sectional view through a rotationallyformed particle mixing system tube in a forming mold;

[0023]FIG. 9 is a perspective view of an alternative embodiment of anair bubble separator; and

[0024]FIG. 10 is a side elevation view of the air bubble separator ofFIG. 9.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0025] A schematic flow diagram for the water treatment system of thisinvention is provided in FIG. 1. Raw influent water is directed into theparticle mixing system 10 (described in detail below) via an inlet pipe12 as indicated by arrow 14 at any suitable pressure, typically 30 psi.Simultaneously a suitable portion of the product water of the system,passing through system outlet pipe 16, is recirculated through pipe 18as indicated by arrows 20 to a pump and flowmeter 22 where pressure issubstantially increased, typically to about 100 psi.

[0026] The high pressure recirculated water passes through pipe 23 to anair contactor arrangement 24 typically including two tanks in series.High pressure air (typically at about 100 psi) is passed from aconventional air compressor 26 through a pipe 28. Air is introduced intothe upstream ends of the tanks forming air contactor 24. The air isdissolved in the high pressure water in air contactor 24. Any suitablemedia may be used in the air contactor tanks to aid in fully saturatingthe air. For optimum operation, hollow membrane fibers of the sortavailable from the Dainippon Ink and Chemical Corporation under theSepareo EF 04P designation are preferred. While air contactor 24preferably comprises two tanks in series, a single tank or more than twotanks may be used, if desired.

[0027] Air saturated water passes out of air contactor 24 through apressure regulator 30 which reduces pressure to a suitable degree. Apressure of 25 to 35 psi is preferred, with about 30 psi being optimum.The air saturated water from air contactor 24 is mixed with the rawwater in particle mixing system 10.

[0028] Particle mixing system 10 as seen in FIG. 2 basically comprises ahelical tube 32 within which the raw water and air saturated watermixes. The diameter of tube 32, the diameter of the helix and the lengthof tube 32 will depend on the volume of water to be treated. In atypical system, tube 32 will have a diameter of from about 4 to 10inches, a length of about 70 to 100 feet, with the helical coil having adiameter of from about 2 to 6 feet.

[0029] In order to achieve optimum turbulence to ideally mix the rawwater and the air saturated water, I have found that a pattern ofdimples 97 (as shown in FIG. 8) should be provided over at least a largeportion of the inner wall surface of tube 32. Also, output pipe 36 fromthe particle mixing system should have these dimples 97 on the interiorwall surface.

[0030] The particle mixing system may be manufactured in any suitablemanner. Preferably, the helical tube arrangement will be formed byconventional rotational casting, using an outer mold half 101 outsidethe helix and an inner helical mold portion 99 within the helix havingraised bumps 97A to create the dimples 97 on the tube, as shown indetail in FIG. 8. Regardless on the manner, the tube 32 may be thussupplied with dimples over almost the entire inner surface. Base 34 thatsupports helical tube 32 may be formed in any suitable manner, such asvacuum forming.

[0031] Returning to FIG. 1, output from helical tube output 36 passesthrough pipe 38 to inlet 40 of air bubble separator 42. Millions of verytiny bubbles will form during mixing in particle mixing system 10 whenpressure drops from typically 100 psi in air contactor 24 to typically30 psi at pressure regulator 30. These tiny bubbles adhere to smalllight weight particles and carry the particles upwardly in air bubbleseparator 42.

[0032] Air bubble separator 42 consists of a lower section 44 as seen inFIGS. 3 and 5, a central section 46 seen in FIGS. 3 and 4 which isgenerally tubular and may be formed from a transparent material such asglass or an acrylic resin to permit observation of flow therethrough andan upper section as seen in FIGS. 3 and 5.

[0033] The mixture of water and air enters tangentially through inlet40, setting up a spinning vortex of water flowing upwardly though centersection 46, creating a boundary-layer transfer effect much like thelaminar flow created as water flows through a pipe. More than one inlet40 may be used if desired. Inlet 40 may have any suitable end or nozzleconfiguration. Each “boundary” layer of water molecules moves slowerbecause of the frictional drag created by the slower moving layerscloser to the center of the column. Heavier particles settle in the sumpat the lower end of the lower section 46 and can be drawn off from timeto time through a drain opening 50. Millions of very tiny bubbles formas the saturated water enters the lower section. The flowing stream ofwater and tiny bubbles has the appearance of milk.

[0034] Velocity of the spiraling white-water stream accelerates as itflows upwardly through the reducing bell-like chamber 52, creating ahigh-pressure zone around the outer parameter of the column and alow-pressure zone in the center of the vortex. Differential pressurebetween the outer wall and the vortex center increases substantially incenter section 46. Boundary layer friction causes the shape of themicroscopic bubbles to flatten. This slower boundary layer frictionaldrag across the bubble's high pressure surface side elongates thebubble, which is pulled towards the center vortex. Flattened microscopicair bubbles passing through multiple boundary layers collide withrelatively stationary suspended particles in the spiraling stream.Positively charged polymers and flocculents and microscopic air bubblesattach to the particles, forcing them to the center. Millions of thesemicroscopic air bubbles “float” horizontally towards the low-pressurecenter of the vortex and tend to coalesce there. This moving “screen” ofmicroscopic bubbles cleans the water in the water annulus and outerperimeter areas as the flow spirals upward.

[0035] Velocity of the spiraling water column is reduced as it entersthe expansion bell chamber 54. Laminar friction holds gases and theconcentrated buoyant float particles near the center of the vortex untilthey reach the top of the column.

[0036] Particles and gases stripped from the clean water around theperimeter of upper section 48 form a concentrated slurry in the centerof the vortex as it enters the float chamber 56. Only small microscopicbubbles remain near the outer diameter as the water column flowsupwardly. As best seen in FIG. 4, a narrow band of water near weir lip58 flows over the edge of the weir lip, exiting through the productwater discharge port 64, typically at a rate of about 50 to 200 gpm.

[0037] The spinning slurry of buoyant suspended particles and airbubbles enters the waste float removal chamber 66 and flows over theedge of waste trough 68, exiting the separator 42 through waste outlet70, typically at about 5 to 20 gpm to wasted disposal through pipe 72(FIG. 1).

[0038] A conventional level controller 74 activates an air relief valve76 at the top of separator 42, regulating the surface level of thewater-air interface inside the top of the water column. Air relief valve76 closes as the water level rises and opens when gasses accumulating atthe top of the column causes the surface water level inside separator 42to drop. This maintains the surface level between broken lines 78,correspondingly between the top and bottom of the waste-float outlet 70.

[0039] Gases exiting through air relief valve 76 pass through pipe 80 toa conventional volatile gas recovery unit 82 (FIG. 1) for recovery,typically with a carbon filter.

[0040] At this point, the water generally has had nearly allcontaminants removed and can be passed to a conventional water plantfiltration system via output pipe to remove any remaining largeparticles. However, in this embodiment a second stage is added as seenin FIG. 1.

[0041] Where the additional cleaning of the water is desired, outputpipe 84 is connected to a second contactor unit 86, basically the sameas air contactor 24. However here air from air compressor 26 is passedto a conventional oxygen concentrator 88. Oxygen concentrator 88increases the proportion of oxygen in the gas to about 60 to 90 percent.Next the gas goes to a conventional corona discharge type ozonegenerator 90 where a suitable percentage of the oxygen is converted toozone. The resulting high ozone gas is fed to contactor 86 at typicallyabout 35 psi, with the water in the contactor typically at about 30 psi.

[0042] As the mixture of water and ozone containing gas is directed to asecond particle mixing system 92, basically the same as particle mixingsystem 10 described above, where hydroxyl radicals (dissolved ozone) aremixed with any remaining suspended particles and non-volatile dissolvedorganic matter.

[0043] The output of second particle mixing system 92 passes throughpipe 93 to a second air bubble separator 94 generally the same as airbubble separator 42, as described above. Preferably, a pattern ofdimples is provided over the internal surface of pipe 93 to increaseturbulence and the resulting improved mixing, as discussed above. Thecoalesced partially oxidized suspended buoyant particles and volatilegases are extracted by the vortex in separator 94 and pass to gasrecovery unit 82 via pipe 96. This prefiltration process removes over85% of the suspended solids from the treatment plant process water flow.Also, substantially all algae is removed. This is sufficient to meetpresent US EPA Clean Water Act regulations for a minimum 85% removal ofsuspended solids. Where further removal is desired, the output waterfrom particle mixing system 92 can be passed through pipe 16 to anyconventional filtration system.

[0044] As mentioned above, I have found that forming a pattern ofdimples on a suitable portion of the interior of tubes 32 in particlemixing systems 10 and 92 and in pipes 38 and 93 will significantlyimprove turbulence therein and greatly improve mixing of water with theadded gases in the two particle mixing systems 10 and 92.

[0045]FIG. 6 illustrates an alternative embodiment using a singlecleaning stage with the saturated air and eliminates the second, ozonetreatment stage shown in FIG. 1.

[0046] As seen in FIG. 2, the air contactor 24, particle mixing system10 and air bubble separator 42 are essentially identical to the firststage of FIG. 1. Air from compressor 26 is directed to air contactor 24together with recirculated water from clean water output line 84 fromair bubble separator 42.

[0047] Saturated water from air contactor 24 passes to particle mixer 10where bubbles form and pick up buoyant particles. Water and bubbles fromair contactor 24 then passes to air bubble separator 42. There, heavyparticles are drained away through drain 50, waste water with buoyantparticles passes out through waste pipe 72 and gasses are passed outthrough pipe 80 to gas recovery unit 82. Clean water passes out throughpipe 84 to and further filtration treatment, storage or use.

[0048] Water is recirculated through pipe 114 to pump 22 and enters aircontactor 24 to continue the process. The clean water from pipe 84 issuitable for many purposes, such as some process water for manufacturingfacilities and the like. For higher purity purposes, the system shown inFIG. 1 is preferred.

[0049]FIG. 7 illustrates an alternate flow path for air and recirculatedwater through the air contactor unit. Each unit 24 comprises a cartridgehaving a very large number of thin, porous, tubes 111 connected to amanifold 113 at the top of each unit 24 so that air enters all of tubes111. Meanwhile, recirculated water enters the top of one unit 24, flowsbetween tubes 111, out the bottom and to the top of the second unit 24through pipe 29, thence between tubes the same as tubes 111 and out thebottom of the second unit 24 via pressure regulator 30 to the particlemixing system 10. Air or oxygen forced, by means of an air compressor 26(as shown in FIGS. 1 and 6), through the open pores in tubes 111 isadsorbed by the recirculating water flow as it passes over the openpores. Conventional sensors 115 at the bottom of units 24 sense anaccumulation of air at the bottom of the unit and open a valve in thesensor to bleed off the air.

[0050]FIGS. 9 and 10 illustrate an alternative embodiment of an airbubble separator system. Here air bubble separator includes a singlepiece, unitary housing 120 preferable formed by conventional rotationalmolding. A base 122 may be formed at the same time housing 120 is formedor may be formed separately and secured to the housing, such as byadhesive bonding. Water from the particle mixing system is injected intothe air bubble separator through a tangential inlet 126. An upperportion 124 of housing 122 has a cylindrical configuration with anoutlet 128 through which clean water is released. At the top is a widertop portion 130, typically 10 to 50% wider than the adjacent upperportion 124, having an outlet 132. Two level sensors 134 are provided intop portion 130 to measure the water level. Typically, level sensors 134may be NK ultrasonic level switches from the Kobold company. A gas vent136 is provided to vent toxic gases and the like. As discussed above,one of sensors 134 will open gas vent 134 when the water level is low torelease gas and the other will close the gas vent when water level ishigh.

[0051] Unit 120 may be formed from any suitable plastic material, suchas a polyolefin or an acrylic. This embodiment is easily and rapidlymanufactured by rotational molding and is highly resistant to corrosionor other damage from constituents of the water mixture being processed.

[0052] Other applications, variations and ramifications of thisinvention will occur to those skilled in the art upon reading thisdisclosure. Those are intended to be included within the scope of thisinvention, as defined in the appended claims.

I claim:
 1. Water decontamination apparatus which comprises: an aircontactor means for introducing air into recirculated water at apressure of at least about 70 psi to substantially saturate watertherein; a particle mixer for receiving and mixing said saturated waterfrom said gas contactor means with influent water containing at leastsome contaminants to be removed; means for directing said water fromsaid air contactor means to said particle mixer at a pressure less thansaid gas contactor pressure so that a plurality of very small bubblesform in said particle mixer; an air bubble separator having a waterinlet adjacent to its bottom for receiving water from said particlemixer; said air bubble separator comprising means for causing vortexrotation of received water for coalescing said bubbles and entrainedparticles along an axis and causing decontaminated water to move alongan outer wall of said air bubble separator; first outlet means forremoving said coalesced bubbles and any entrained particles; secondoutlet means from said air bubble separator for removing saiddecontaminated water; means for removing gases from said bubbleseparator; and means for directing a portion of said decontaminatedwater from said second outlet to said air gas contactor means as saidrecirculated water.
 2. The apparatus according to claim 1 wherein saidgas contactor means includes a plurality of hollow porous tubes andincludes means for directing said air into said tubes and saidrecirculated water into spaces between said tubes so that said air movesthrough said porous tubes and is adsorbed by said recirculated water. 3.The apparatus according to claim 1 further including a pressureregulator for maintaining pressure at a predetermined level in said gascontactor means prior to passage of said saturated water to saidparticle mixer.
 4. The apparatus according to claim 3 wherein saidpressure is maintained at about 100 psi.
 5. The apparatus according toclaim 1 wherein said particle mixer comprises an elongated helical tubecoil, the internal surface of said tube coil having a predeterminedpattern of dimples over at least a portion of said surface.
 6. Theapparatus according to claim 1 wherein said air bubble separatorcomprises a vertically oriented tube having a central axis, an outerwall and upper and central sections above said lower section with awater outlet in said upper section.
 7. The apparatus according to claim6 wherein said water inlet is oriented at a predetermined angle so thata rotating water vortex is formed and said lower section comprises asump below said water inlet for collecting heavy particles and a drainfor periodically removing said heavy particles.
 8. The apparatusaccording to claim 6 wherein said central section has a diameter lessthan that of the upper and lower sections and includes gradualtransitions therebetween.
 9. The apparatus according to claim 6 whereinsaid upper section includes a weir over which water rotating in saidvortex along said outer wall flows into a circumferential product troughand a water outlet means for removing water from said product trough.10. The apparatus according to claim 6 wherein said upper sectionfurther includes a waste trough for receiving floating waste and a wasteoutlet means for removing said floating waste.
 11. The apparatusaccording to claim 6 wherein said upper section includes a gas reliefmeans for removing gases from said upper section and level controllermeans for maintaining a predetermined water level in said upper section.12. The apparatus according to claim 6 wherein said particle separatoris a unitary rotationally molded structure comprising a tubular columnhaving a central region narrower than end regions, an approximatelycylindrical upper section having an outlet for decontaminated water, anapproximately cylindrical top section having an outlet for coalesced airbubbles and entrained contaminants.
 13. The apparatus according to claim12 further including a gas relief valve in said top section forreleasing gases.
 14. The apparatus according to claim 13 furtherincluding level sensor means for sensing the level of water in said topsection and for opening said valve when water level reaches apredetermined low level and for closing said valve when water levelreaches a predetermined high level.
 15. The apparatus according to claim1 further including air compressor means for supplying air at apredetermined pressure to said gas contactor means.
 16. The apparatusaccording to claim 1 wherein said means for directing water from saidparticle mixer to said air bubble separator comprises pipes having aninternal surface with dimples over at least a portion thereof.
 17. Waterdecontamination apparatus which comprises: a first gas contactor meansfor introducing air into recirculated water at a pressure of at leastabout 70 psi to substantially saturate water therein; a first particlemixer for forming a mixture of saturated water from said first gascontactor means with influent water containing at least some particlesto be removed; means for directing said saturated water from said firstgas contactor means to said first particle mixer; means for directingsaid influent water to said first particle mixer at a pressure less thansaid first gas contactor pressure so that a plurality of very smallbubbles form in said particle mixer; a first air bubble separator havinga water inlet adjacent to its lower section for receiving said mixedwater from said first particle mixer; said first air bubble separatorcomprising means for causing vortex rotation around an axis of receivedwater for coalescing said bubbles along said axis; means for removingsaid coalesced bubbles and any entrained material from said first airbubble separator; first water outlet means from said first air bubbleseparator; means for removing gases from said bubble separator; and asecond gas contactor means for receiving water from said first wateroutlet means; means for introducing a gas comprising oxygen and ozoneinto a second gas contactor means to produce a plurality of very smalldissolved bubbles; a second particle mixer for receiving water from saidsecond gas contactor means; a second bubble separator comprising meansfor coalescing said bubbles along an axis; second means for removingsaid coalesced bubbles and any entrained material; second outlet meansfor removing treated water from said second bubble separator; and meansfor directing a predetermined portion of said treated water back to saidfirst particle mixer as said recirculated water.
 18. The apparatusaccording to claim 17 wherein said gas contactor means includes aplurality of hollow porous tubes and includes means for directing saidair into said tubes and said recirculated water into spaces between saidtubes so that said air moves through said porous tubes and is adsorbedby said recirculated water.
 19. The apparatus according to claim 17further including a pressure regulator for maintaining pressure at apredetermined level in said means for directing water from each of saidfirst and second gas contactor means to said first and second particlemixers, respectively.
 20. The apparatus according to claim 19 whereinsaid pressure is maintained at about 100 psi.
 21. The apparatusaccording to claim 17 wherein each of said first and second particlemixers comprises an elongated helical tube coil, the internal surface ofsaid tube coil having a predetermined pattern of dimples over at least aportion of said internal surface.
 22. The apparatus according to claim17 wherein said first and second bubble separators each comprises avertically oriented tube having a central axis, an outer wall and upperand central sections above said lower section with a water outlet insaid upper section.
 23. The apparatus according to claim 17 wherein eachsaid water inlet is oriented at a predetermined angle so that a rotatingwater vortex is formed and said each said lower section comprises a sumpbelow said water inlet for collecting heavy particles and a drain forperiodically removing said heavy particles.
 24. The apparatus accordingto claim 17 wherein each said first and second central sections has adiameter less than that of the upper and lower sections and includesgradual transitions therebetween.
 25. The apparatus according to claim17 wherein each said first and second upper sections includes a weirover which water rotating in said vortex along said outer wall flowsinto a circumferential product trough and a water outlet means forremoving water from said product trough.
 26. The apparatus according toclaim 17 wherein each said first and second upper section furtherincludes a waste trough for receiving floating waste and a waste outletmeans for removing said floating waste.
 27. The apparatus according toclaim 17 wherein each said first and second upper sections includes agas relief means for removing gases from said respective upper sectionsand level controller means for maintaining a predetermined water levelin said respective upper sections.
 28. The apparatus according to claim17 further including air compressor means for providing high pressureair to said first and second gas contactor means and including oxygenconcentrating means and ozone generator means between said aircompressor and said second gas contactor means.
 29. The apparatusaccording to claim 17 wherein said means for directing water from eachsaid first and second particle mixers to each said first and second gasbubble separators comprises pipes having an internal surface withdimples over at least a portion thereof.
 30. The apparatus according toclaim 17 wherein said particle separator is a unitary rotationallymolded structure comprising a tubular column having a central regionnarrower than end regions, an approximately cylindrical upper sectionhaving an outlet for decontaminated water, an approximately cylindricaltop section having an outlet for coalesced air bubbles and entrainedcontaminants.
 31. The apparatus according to claim 30 further includinga gas relief valve in said top section for releasing gases.
 32. Theapparatus according to claim 30 further including level sensor means forsensing the level of water in said top section and for opening saidvalve when water level reaches a predetermined low level and for closingsaid valve when water level reaches a predetermined high level.
 33. Amethod of removing contaminants from water which comprises the steps of:directing recirculated first product water into an air contacting means;directing air at a pressure of at least about 70 psi into said aircontacting means to at least partially saturate said recirculated water;directing said at least partially saturated water to a particle mixer;directing influent water containing at least some organic particles tosaid particle mixer; mixing said at least partially saturated water andsaid influent water while reducing pressure to allow a plurality of verysmall air bubbles to form in the resulting mixture and to entrainparticles; directing said mixture to an air bubble separator; causingsaid mixture to rotate about an axis in said air bubble separator sothat said bubbles coalesce along said axis with first product waterspaced from said axis; removing said coalesced bubbles and entrainedsolid material; and removing said first product water and recirculatinga portion of said first product water.
 34. The method according to claim33 wherein said mixing is increased by causing turbulent flow overdimples in walls of said particle mixer.
 35. The method according toclaim 33 further including regulating pressure of water passing fromsaid air contacting means to said particle mixer to a predeterminedlevel at least about 70 psi.
 36. The method according to claim 35wherein said pressure is regulated to approximately 100 psi.
 37. Themethod according to claim 33 further including collecting heavyparticles at a lower end of said air bubble separator.
 38. The methodaccording to claim 33 further including removing air bubbles and buoyantparticles from a predetermined location at about an upper end of saidair bubble separator.
 39. The method according to claim 38 furtherincluding removing air and any gases present from an upper end of saidair bubble separator above said predetermined location.
 40. The methodaccording to claim 39 further including maintaining an interface betweensaid bubbles and buoyant particles and said air and gases at apredetermined level.
 41. A method of removing contaminants from waterwhich comprises the steps of: directing recirculated second productwater into a first air contacting means; directing air at a pressure ofat least about 70 psi into said first air contacting means to at leastpartially saturate said recirculated water; directing said at leastpartially saturated water to a first particle mixer; directing influentwater containing at least some organic particles to said first particlemixer; mixing said at least partially saturated water and said influentwater while reducing pressure to allow a plurality of very small airbubbles to form in the resulting first mixture and to entrain particles;directing said first mixture to a first air bubble separator; causingsaid first mixture to rotate about an axis in said air bubble separatorso that said bubbles coalesce along said axis with first product waterspaced from said axis; removing said coalesced bubbles and entrainedsolid material; directing said first product water to a second aircontacting means; directing air at a pressure of at least about 30 psiinto an oxygen concentrator to increase the proportion of oxygentherein; directing gas from said oxygen concentrator to an ozonegenerator to increase the proportion of ozone therein to a predeterminedextent; directing gas from said ozone generator into a second aircontacting means to at least partially saturate said first productwater; directing said at least partially saturated first product waterto a second particle mixer; mixing said at least partially saturatedfirst product water while reducing pressure to allow a plurality of verysmall air bubbles to form in the resulting second mixture and to entrainparticles; directing said second mixture to a second air bubbleseparator; causing said mixture to rotate about an axis in said secondair bubble separator so that said bubbles coalesce along said axis witha second product water spaced from said axis; removing said coalescedbubbles and entrained solid material; and removing said second productwater.
 42. The method according to claim 41 wherein said mixing in eachof said first and second particle mixers is increased by causingturbulent flow over dimples in walls of said particle mixers.
 43. Themethod according to claim 41 further including regulating pressure ofwater passing from each of said first and second air contacting means tosaid first and second particle mixers, respectively, to a predeterminedlevel at least about 70 psi.
 44. The method according to claim 43wherein said pressure is regulated to approximately 100 psi.
 45. Themethod according to claim 41 further including collecting heavyparticles at a lower end of each of said first and second air bubbleseparators.
 46. The method according to claim 41 further includingremoving air bubbles and buoyant particles from a predetermined locationat about an upper end of each of said first and second air bubbleseparators.
 47. The method according to claim 42 further includingremoving air and any gases present from an upper end of each of saidfirst and second air bubble separator above said predetermined location.48. The method according to claim 47 further including maintaining aninterface between said bubbles and buoyant particles and said air andgases at a predetermined level.
 49. A particle mixer for use in a waterdecontamination system, which comprises; an elongated helical tube;first inlet means for admitting a first water selected from the groupconsisting of at least partially decontaminated, at least partially airsaturated, water at a pressure of at least about 70 and at leastpartially decontaminated, partially ozone saturated, into an inlet endof said elongated helical tube; second inlet means for introducing asecond, raw, water at lower pressure than that of said liquid into saidtube to mix said first and second water; whereby a plurality of verysmall gas bubbles spontaneously form in the resulting mixed water; anoutlet pipe for removing said resulting mixture of mixed water and smallgas bubbles; at least a portion of the interior surface of said tubebears a plurality of spaced dimples turbulence inducing.
 50. Theparticle mixer according to claim 49 further including a plurality ofsaid dimples in the interior surface of said outlet pipe.
 51. An airbubble separator for use in a water decontamination system, whichcomprises: an elongated, tubular, housing having an inner wall and acentral axis; water inlet means adjacent a first end of said housing fordirecting a mixture of water, bubbles and contaminants into saidhousing; means for causing vortex rotation of received water forcoalescing said bubbles along said axis and causing decontaminated waterto flow along said inner wall; means for removing said coalesced bubblesand any buoyant entrained material from said housing; means for removingdecontaminated water from said housing; means for removing gases fromsaid housing.
 52. The air bubble separator according to claim 51 whereinsaid housing comprises an inlet section, a central section and an outletsections with a contaminated water inlet in said inlet section forreceiving water from said particle mixer and a decontaminated wateroutlet in said outlet section.
 53. The air bubble separator according toclaim 52 wherein said water inlet means for directing said water fromsaid particle mixer is oriented at a predetermined angle to said axis sothat a rotating water vortex is formed.
 54. The air bubble separatoraccording to claim 52 further including a sump adjacent to said waterinlet, opposite said central section, for collecting heavy particles anda drain for periodically removing said heavy particles.
 55. The airbubble separator according to claim 52 wherein said central section hasa diameter less than that of the outlet and inlet sections and includesgradual transitions therebetween.
 56. The air bubble separator accordingto claim 52 wherein said outlet section includes a weir over which waterrotating in said vortex along said outer wall flows into acircumferential product trough between said outer wall and weir whichcommunicates with said water outlet for removing water from said producttrough.
 57. The air bubble separator according to claim 52 wherein saidoutlet section further includes a waste trough for receiving a mixtureof bubbles and buoyant waste and a waste outlet means for removing saidfloating waste.
 58. The air bubble separator according to claim 52wherein said outlet section includes a gas relief means for removinggases from said outlet section and level controller means formaintaining a predetermined water level in said outlet section.
 59. Theair bubble separator according to claim 52 wherein said column is aunitary plastic structure formed by rotational molding.
 60. The airbubble separator according to claim 59 wherein said housing comprises aninlet section, a central section and an outlet sections with acontaminated water inlet in said inlet section for receiving water fromsaid particle mixer, a approximately cylindrical first portion of saidoutlet section having a decontaminated water outlet and an approximatelycylindrical second portion of said outlet section having an outlet forcoalesced bubbles and any entrained particles therewith.
 61. The airbubble separator according to claim 59 wherein said second portion has adiameter from about 10 to 25 per cent greater than the diameter of saidfirst portion.